@article {434, title = {Rotational diffusion measurements of suspended colloidal particles using two-dimensional exchange nuclear magnetic resonance}, journal = {Journal of Chemical Physics}, volume = {104}, year = {1996}, note = {J Chem PhysTn837Times Cited:13Cited References Count:24}, month = {Jan 8}, pages = {509-520}, abstract = {

We present here an experimental and theoretical study of the application of two-dimensional exchange nuclear magnetic resonance spectroscopy (NMR) to the investigation of the rotational diffusion of colloidal particles. The theoretical discussion includes the nature of the NMR frequency time-correlation function where the NMR interaction is represented by the chemical shift anisotropy (CSA). Time-correlation functions for the isotropic rotational diffusion of a suspension of colloidal particles containing single and multiple sites are derived in addition to time-correlation functions for the rotational diffusion of a suspension of symmetric top particles containing an isotropic distribution of a single CSA interaction. Simulations of two-dimensional exchange spectra for particles undergoing isotropic rotational diffusion are presented. We performed two-dimensional exchange NMR experiments on a colloidal suspension of spherical poly(methyl methacrylate) (PMMA) particles which were synthesized with a 20\% enrichment in C-13 at the carbonyl site. Rotational diffusion time-correlation functions determined from the experimental exchange spectra are consistent with the composition of the colloidal suspension. Detailed explanations of the syntheses of the enriched methyl C-13-(carbonyl)-methacrylate monomer and the small quantities of 20\% enriched C-13-(carbonyl)-poly(methyl methacrylate) microspheres used for this study are presented. (C) 1996 American Institute of Physics.

}, keywords = {scattering}, isbn = {0021-9606}, doi = {Doi 10.1063/1.470847}, url = {://WOS:A1996TN83700009}, author = {Barrall, G. A. and Schmidt-Rohr, K. and Lee, Y. K. and Landfester, K. and Zimmermann, H. and Chingas, G. C. and Pines, A.} } @article {449, title = {C-13 Chemical-Shift Tensor Correlation Via Spin-Diffusion in Solid Tropolone Using Switched-Angle Spinning Spectroscopy}, journal = {Journal of Chemical Physics}, volume = {103}, year = {1995}, note = {J Chem PhysTh657Times Cited:7Cited References Count:42}, month = {Dec 8}, pages = {9844-9854}, abstract = {

In switched-angle spinning spectroscopy (SAS) a sample is spun about different angles, beta, relative to the magnetic field, during various periods of the experiment. In the present work, SAS is combined with two-dimensional exchange spectroscopy in order to correlate carbon-13 chemical shift tensors of the carbonyl (1) and hydroxyl (2) carbons of tropolone. Experiments were performed on a sample enriched to 25 at. \% in each of these sites (at different molecules). At this level of enrichment the dominant exchange mechanism between the two sites involves spin diffusion, The experiment consists of a preparation period during which the sample spins at the magic angle and the magnetization of one of the sites is quenched by means of a selective pulse sequence. During the rest of the experiment the sample spins with its axis away from the magic angle except for a short period just before the detection where the axis is switched to the magic angle in order to select the magnetization to be detected. Experiments were performed for all four possible combinations of the initial and final magnetizations, thus providing chemical shift correlations between carbons 1,1\&$\#$39;,2, and 2\&$\#$39; in the two magnetically inequivalent (but symmetry related) molecules in the unit cell. Combining these results with the known crystal structure of tropolone (neglecting a small tilt between the perpendicular to the molecular plane and the crystallographic c-axis) provides information on the orientation and magnitude of the chemical shift tensors of the two types of carbons, The principal values (in ppm) are sigma(xx)(1)=65, sigma(yy)(1)=33, sigma(zz)(1)=-98, sigma(xx)(2)=77, sigma(yy)(2)=17, and sigma(zz)(2)=-94. Assuming sigma(zz) to be perpendicular to the molecular plane, the orientations of the sigma(yy) s\&$\#$39; are 12 degrees off the C-1=0 bond (toward the hydroxyl carbon) for carbon 1 and 10 degrees off the C-3=C-2 bond (away from the carbonyl carbon) for carbon 2. (C) 1995 American Institute of Physics.

}, keywords = {spectra}, isbn = {0021-9606}, doi = {Doi 10.1063/1.469951}, url = {://WOS:A1995TH65700040}, author = {Larsen, R. G. and Lee, Y. K. and He, B. and Yang, J. O. and Luz, Z. and Zimmermann, H. and Pines, A.} } @article {592, title = {Assignment of Dipolar Couplings and Estimation of Conformational Probabilities in Partially Oriented Hexane}, journal = {Chemical Physics Letters}, volume = {137}, year = {1987}, note = {Chem Phys LettH6843Times Cited:19Cited References Count:19}, month = {May 29}, pages = {51-56}, isbn = {0009-2614}, doi = {Doi 10.1016/0009-2614(87)80303-2}, url = {://WOS:A1987H684300012}, author = {Gochin, M. and Zimmermann, H. and Pines, A.} } @article {593, title = {Two-Dimensional Multiple Quantum Nmr of Isotopic Mixtures in Liquid-Crystals}, journal = {Molecular Physics}, volume = {60}, year = {1987}, note = {Mol PhysF9930Times Cited:12Cited References Count:18}, month = {Jan}, pages = {205-212}, isbn = {0026-8976}, doi = {Doi 10.1080/00268978700100151}, url = {://WOS:A1987F993000015}, author = {Gochin, M. and Hugicleary, D. and Zimmermann, H. and Pines, A.} } @article {609, title = {Determination of Dipole Dipole Couplings in Oriented Normal-Hexane by Two-Dimensional Nmr}, journal = {Journal of the American Chemical Society}, volume = {108}, year = {1986}, note = {J Am Chem SocE5180Times Cited:22Cited References Count:17}, month = {Oct 15}, pages = {6813-6814}, isbn = {0002-7863}, doi = {Doi 10.1021/Ja00281a064}, url = {://WOS:A1986E518000064}, author = {Gochin, M. and Schenker, K. V. and Zimmermann, H. and Pines, A.} } @article {606, title = {High-Resolution Studies of Deuterium by Time-Domain Zero-Field Nqr}, journal = {Journal of Magnetic Resonance}, volume = {69}, year = {1986}, note = {J Magn ResonE1115Times Cited:11Cited References Count:49}, month = {Sep}, pages = {243-257}, isbn = {1090-7807}, doi = {Doi 10.1016/0022-2364(86)90076-4}, url = {://WOS:A1986E111500005}, author = {Millar, J. M. and Thayer, A. M. and Zimmermann, H. and Pines, A.} } @article {635, title = {Fourier-Transform Pure Nuclear-Quadrupole Resonance by Pulsed Field Cycling}, journal = {Journal of Chemical Physics}, volume = {80}, year = {1984}, note = {J Chem PhysSh432Times Cited:34Cited References Count:23}, pages = {2232-2234}, isbn = {0021-9606}, doi = {Doi 10.1063/1.446915}, url = {://WOS:A1984SH43200068}, author = {Bielecki, A. and Murdoch, J. B. and Weitekamp, D. P. and Zax, D. B. and Zilm, K. W. and Zimmermann, H. and Pines, A.} }